1. Field of the Invention
This invention is directed to producing highly concentrated solutions of the bifunctional monomer methylenebisacrylamide (CH.sub.2 .dbd.CHCONH).sub.2 CH.sub.2, and thereafter for example blending them with ionogenous acrylic monomers to produce homogeneous solutions which are polymerized to produce low porosity, highly crosslinked, water insoluble polymers for use as anion selective resins and membranes.
2. Description of the Prior Art
The usual technique for the production of anion selective polymers similar to those described in the invention involves co-polymerizing methacrylate esters containing amine groups of the tertiary type, with crosslinking methacrylate esters (U.S. Pat. No. 4,231,855 Hodgdon et. al.). The resulting polymer with pendant tertiary amine groups is further reacted so that the tertiary amine groups are converted to quaternary ammonium salts producing an anion selective membrane structure. This prior art has disadvantages in that the polymerization reaction is carried out in non-water soluble organic solvents that have to be washed out with a water soluble alcohol (such as methanol) before the polymer membrane sheet can be subjected to quaternization to the ammonium salt. A further disadvantage of the prior art is the use of acrylate esters which degrade rapidly in the presence of caustic substances such as sodium hydroxide solutions. The present invention comprises an improvement over methods of the prior art by using water soluble polar solvents and monomers possessing acrylamide groups, (which are only slightly sensitive to caustic solutions) thus replacing the use of acrylate ester groups. Further, the present invention comprises a method to obtain concentrated solutions of methylenebisacrylamide (MBA) in water soluble, polar solvents using caustic as a solubilizing agent. Prior art methods utilizing methylenebisacrylamide are generally limited by the poor solubility of methylenebisacrylamide in the commonly employed solvents.